1. Field of the Invention
The invention relates to a touch and proximity sensing device, and more particularly to a touch and proximity sensing device using only one sensed signal conversion engine.
2. Description of the Related Art
Conventionally, a traditional mechanical button device applied to electronic products uses mechanical buttons to control activation and deactivation of an electrical circuit.
With progress of technology, the traditional mechanical buttons which are bulky and require individual assembly have become unsuited for use in a current electronic product which tends to be light, thin, short, and small. Moreover, touch sensing techniques have become mature, and traditional mechanical buttons are gradually being replaced by sensing buttons in electronic products.
Two types of conventional touch and proximity sensing devices are described hereinbelow.
Referring to FIGS. 1 to 3, a first type of the touch and proximity sensing devices includes a circuit board 11 and two sensed signal processing units 12. Each sensed signal processing unit 12 includes a sensed signal conversion engine 121 disposed on a bottom surface of the circuit board 11. Each sensed signal processing unit 12 may be a signal processing chip. The circuit board 11 includes a substrate 111, a plurality of capacitor sensing electrodes 112, a proximity sensing electrode 113, and a grounding conductive film 114. The capacitor sensing electrodes 112 and the proximity sensing electrode 113 are disposed on a top surface of the substrate 11, and the sensed signal conversion engines 121 and the grounding conductive film 114 are disposed on the bottom surface of the substrate 111. One of the sensed signal conversion engines 121 is coupled to the capacitor sensing electrodes 112, and the other one of the sensed signal conversion engine 121 is coupled to the proximity sensing electrode 113. The grounding conductive film 114 is correspondingly disposed under the capacitor sensing electrodes 112 and the proximity sensing electrode 113.
External electric power is provided to the capacitor sensing electrodes 112 and the proximity sensing electrode 113 via the sensed signal conversion engines 121. When one of the capacitor sensing electrodes 112 is touched or a finger is located in a sensing range of the proximity sensing electrode 113, one of the sensed signal conversion engines 121 detects variation of an electric signal from said one of the capacitor sensing electrodes 112, or the other one of the sensed signal conversion engines 121 detects variation of an electric signal from the proximity sensing electrode 113. Then, execution of relevant external process is driven through the sensed signal conversion engine 121, such as turning on light emitting diodes disposed on the circuit board 11 (not shown).
Since the signals from the capacitor sensing electrodes 112 and the proximity sensing electrode 113 easily interfere with each other, the first type of the touch and proximity sensing devices separately processes the two different kinds of the signals using two independent sensed signal conversion engines 121 to reduce interference level therebetween, so that the sensed signal processing unit 12 must include two independent sensed signal conversion engines 121.
Referring to FIGS. 1, 4, and 5, the second type of the touch and proximity sensing devices includes a circuit board 11 and a sensed signal processing unit 13 disposed on a bottom surface of the circuit board 11. The sensed signal processing unit 13 includes a sensed signal conversion engine 131 and a microcontroller 132 coupled to the sensed signal conversion engine 131. The sensed signal processing unit 13 may be a signal processing chip. The circuit board 11 includes a substrate 111, a plurality of capacitor sensing electrodes 112, a proximity sensing electrode 113, and a grounding conductive film 114. The capacitor sensing electrodes 112 and the proximity sensing electrode 113 are disposed on a top surface of the substrate 111, and the grounding conductive film 114 is disposed on the bottom surface of the substrate 111. The microcontroller 132 is also coupled to the capacitor sensing electrodes 112 and the proximity sensing electrode 113. The grounding conductive film 114 is correspondingly disposed under the capacitor sensing electrodes 112 and the proximity sensing electrode 113.
When external electric power is provided to the sensed signal processing unit 13, the sensed signal conversion engine 131 is controlled by the microcontroller 132 to continuously switch for alternatively receiving signals from the capacitor sensing electrodes 112 or from the proximity sensing electrode 113. When one of the capacitor sensing electrodes 112 is touched or a finger is located in a sensing range of the proximity sensing electrode 113, the sensed signal conversion engine 131 detects variation of an electric signal, which has a magnitude greater than a predetermined threshold value, from said one of the capacitor sensing electrodes 112, or the proximity sensing electrode 113. Then, execution of relevant external process is driven, such as turning on light emitting diodes disposed on the circuit board (not shown).
The sensed signal conversion engine 131 of the second type of the touch and proximity sensing devices is controlled by the microcontroller 132 to switch between a first mode of receiving electric signal from the capacitor sensing electrodes 112 and a second mode of receiving electric signal from the proximity sensing electrode 113, so as to reduce interference level between two different kinds of signals.
However, the first type of the touch and proximity sensing devices requires a lot of area on the circuit board 11 for placement of the two signal processing chips that respectively have a sensed signal conversion engine 121. Even though the two sensed signal engines 121 may be integrated in a signal processing chip, it results in a higher cost and a larger volume of the signal processing chip. The second type of the touch and proximity sensing devices requires a microcontroller 132 embedded in the signal processing chip, and a complicated firmware is required to be written in the signal processing chip for enabling the sensed signal conversion engine 131 to switch between the first and second modes. The additional cost attributed to the microcontroller 132 is thus added to the cost of the second type of the touch and proximity sensing devices. Furthermore, the complicated firmware may have errors, and the continuous switching may result in higher power consumption and heat dissipation issues.